Many large scale military and commercial navigation systems use software to arrive at navigation solutions. Inertial data from inertial measurement units (IMUs) are provided to the software, and based on the inertial data, the software determines position, velocity, attitude, and other parameters used to navigate vehicles such as missiles, aircraft, and spacecraft. The software associated with the navigation systems has often undergone very extensive and expensive verification and qualification—particularly for weapons or aircraft systems—to ensure that the navigation system achieves reliable navigation solutions as designed. The IMU is typically external to the navigation processing system executing the software and communicates the inertial measurement data to the software via an IMU interface. Performing inertial measurement functions with a device external to the navigation processing system affords system designers some flexibility in their choice of, and replacement of, IMUs for use in the systems because the IMU can be replaced without the need to revalidate the navigation processing system's software.
In order to update such navigation processing systems (hereinafter referred to as “legacy” systems) to create potentially more accurate systems, system designers find themselves having to add additional hardware and create new interfaces for their legacy systems, and significantly alter their existing software—all at great delay and expense. This is because the legacy systems and software are designed based on legacy IMU interfaces, which receive inertial measurement data in the form of changes in velocity (typically denoted by Δv) and changes in angle (typically denoted by Δθ). For example, adding a global navigation satellite system (GNSS) receiver to a legacy system is one way to obtain improved positioning solution performance. The problem is that GNSS receivers output data in the form of position and velocity rather than in the form of changes in velocity (Δv) and changes in angle (Δθ). Modification of the legacy system's software to accommodate the GNSS receivers output data would require re-verification and re-qualification of the navigation processing systems. The added expenses for this redesign and retesting tends to offset the possibility of achieving improved performance at the relatively small cost of an added GNSS receiver.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for systems and methods for improved inertial navigation.